configure.ac: check clock_gettime for glib < 2.17
glib < 2.17 doesn't support clock_gettime directly, it is available
via librt.
Change-Id: Ice853d85ffe859b1d4df48b91b050c24d85c861b
diff --git a/src/Makefile.am b/src/Makefile.am
index e9db32f..dca5865 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -12,7 +12,7 @@
lib_LTLIBRARIES = libosmocore.la
-libosmocore_la_LIBADD = $(BACKTRACE_LIB) $(TALLOC_LIBS)
+libosmocore_la_LIBADD = $(BACKTRACE_LIB) $(TALLOC_LIBS) $(LIBRARY_RT)
libosmocore_la_SOURCES = timer.c timer_gettimeofday.c timer_clockgettime.c \
select.c signal.c msgb.c bits.c \
bitvec.c bitcomp.c counter.c fsm.c \